Australia's general election is "too close to call" and the final result may not be known for days as counting continues for tightly contested seats, Labor Party leader and opposition challenger Bill Shorten has said.

With 75.2 percent of the votes cast, the Liberal-National coalition is leading with 72 seats and the Labor Party is close behind with 66, the Australian Broadcasting Corporation has reported.

Seven seats are not decided and other parties, including independents hold five.

For a majority, 76 seats are needed. In the previous election, the coalition had 90. If either party doesn't receive enough votes, support would be needed from other parties/independents.

The hotly contested general election, in which some 15.6 million people were expected to cast their ballots in a compulsory vote across Australia, capped off an extraordinarily volatile period in the country's politics.

Australian political parties can change their leaders under certain conditions and have done so in recent years with unprecedented frequency - a sign of the country's recent political instability.

The ongoing political turmoil, coupled with the global uncertainty brought about by Britain's recent vote to leave the EU, prompted Turnbull, the prime minister, to urge voters to stick with the status quo.

"In an uncertain world, Labor offers only greater uncertainty," Conservative leader Malcolm Turnbull warned in one of his final pitches to voters this week. "They have nothing to say about jobs, growth or our economic future."

Labor, meanwhile, sought throughout the eight-week campaign to cast Turnbull's Liberal Party as deeply divided, with Shorten saying: "You cannot have stability without unity".

Peter Hartcher, political editor at the Sydney Herald, said: "It's more likely that Turnball will hang onto power with a much reduced majority.

"The country is having a great deal of trouble putting its trust in either of the parties. The incumbent government is portraying it as a question of, almost entirely, economics."

'It's embarassing'

Selling stability is a tough job for either party, both of which have been marred by infighting in recent years.

Shorten played a key role in ousting two of the Labor Party's own prime ministers in the space of three years, and Turnbull himself ousted Tony Abbott as prime minister in an internal party showdown less than a year ago. Up until 2007, conservative John Howard served as prime minister for nearly 12 years.

Many voters seemed weary of the constant change.

Morag McCrone, who voted for Labor in Sydney, acknowledged her choice could lead to yet another new prime minister, but could not bring herself to vote for Turnbull's party.

"I'm getting a little bit sick of it," Reid said. "Not to say that John Howard was a great prime minister, but it was good to have someone who was at the helm for a period that wasn't two [or] three years."

Though the race is tight, polls suggest that Labor will not be able to gain the 21 seats it needs to form a majority government in the 150-seat House of Representatives - Labor currently holds 55 seats, the conservative coalition has 90, while minor parties and independents have five.

Results published by market researcher Newspoll in The Australian newspaper on Saturday showed the coalition leading by 50.5 percent to Labor's 49.5 percent. The poll was based on interviews with 4,135 people conducted between Tuesday and Friday, and has a 3 percentage point margin of error.

Opinion polls have also suggested the public's frustration with Labor and the coalition may prompt an unusually high number of votes for minor parties, such as the Greens.

That raises the prospect that neither Labor, nor the coalition, will end up with enough seats to win an outright majority, resulting in a hung parliament.

Economic growth debate

The government has focused much of its campaign on a promise to generate jobs and economic growth through tax cuts to big businesses.

Economic growth is a key issue for many Australians, who have seen thousands of jobs vanish from the country's once-booming resources sector amid China's industrial slowdown.

Labor has said it will keep the higher tax rates and use the revenue to better fund schools and hospitals.

Same-sex marriage has also emerged as a campaign issue.

Turnbull, who personally supports gay marriage despite his party's opposition to it, has promised to hold a national poll known as a plebiscite this year that will ask voters whether the nation should allow same-sex marriage.

But governments are not bound by the results of plebiscites, and some conservative politicians have said they will vote down a gay marriage bill - even if most Australians supported marriage equality.

Labor, which dubbed the plebiscite a waste of taxpayers' money, promises that the first legislation the party will introduce to parliament will be a bill legalising same-sex marriage.